1. Field of the Invention
This invention relates to an improved charge-sensitive recording material having certain ohmic resistivity and providing increased speed. It also relates to a process for providing development of a latent image in the described charge-sensitive recording material. One aspect of the invention relates to use of an electrically activated recording layer comprising a particular image-forming combination with specific speed-increasing electron acceptors to provide a developable latent image.
2. Description of the State of the Art
A variety of recording materials and processes have been proposed and developed to provide image recording. The better known and commercially more successful of these recording materials and processes can be classified as being photographic, thermographic or electrographic or as being a combination of two or more of these. For example, one recording material which is known is a photothermographic material which is a heat developable, photographic material designed for imaging by what has been described as dry processing with heat. Each of the known image recording materials and processes has certain advantages for particular uses; but, the materials and processes also suffer from disadvantages which limit the usefulness in other applications. For example, conventional photographic materials have the disadvantage that they are not room light handleable prior to imagewise exposure and processing. Thermographic materials require imagewise heating to provide a visible image and are not capable of the degree of light sensitivity provided by conventional photographic materials and photothermographic materials. Electrographic materials including, for example, xerographic materials require a mechanical dust pattern transfer procedure in order to provide a desired image.
It has been desirable to provide an image-recording material and process which enable the image density of a developed silver image with increased speed while avoiding the expense of conventional photosensitive silver halide materials and at the same time (1) avoiding the need for conventional processing baths and solutions and (2) enabling room light handling of the imaging material prior to imagewise exposure.
Heat developable photographic materials, or photothermographic materials, which after imagewise exposure can be heated to provide a developed image in the absence of processing solutions or baths are known. These photosensitive materials have the disadvantage that they are not room light handeable prior to imagewise exposure for recording purposes.
Dry electrographic recording materials and processes for the production of a visible image in a charge-sensitive recording element have been described in French Patent No. 2,280,517 published Feb. 27, 1976. These dry electrographic recording materials and processes provide certain advantages, for instance, the use of light handeable materials prior to imagewise exposure. A continuing need has existed, however, to provide increased speed in such materials to provide a developed image within shorter exposure time. This shorter exposure time is especially important, for instance, in X-ray imaging. Shorter X-ray exposure time in X-ray imaging of parts of the human body, for instance, can reduce risk of damage to body tissue.
Other dry electrographic recording materials and processes are also known, such as described in U.S. Pat. No. 3,978,335 of Gibbons, issued Aug. 31, 1976. These materials and processes are satisfactory for many purposes in X-ray imaging. A speed-increasing component which provides at least two times the speed of the described materials would be very useful in these materials. This could expand the purposes and usefulness of the described materials and processes.
Non-silver dry electrographic recording materials and processes have also been proposed as described in copending U.S. Application Ser. No. 783,577 of Lelental and Gysling, filed Apr. 1, 1977. These non-silver electrographic recording materials and processes can provide a visible non-silver image in a charge-sensitive recording element. However, a need has also existed for increased speed in these non-silver electrographic recording materials and processes.
There has also been a continuing need to provide improved tellurium-containing, heat-developable imaging materials and processes in which illumination of silver in the image-recording material provides increased speed to the tellurium-containing material. This continuing need has been especially true for tellurium-containing, heat developable materials which enable amplification of a nuclei image.
A further particular need has continued for an imaging material, preferably a non-silver imaging material, which is room light handleable and suitable for providing increased speed for radiography, such as medical radiography. In this use it is important that as little X-ray radiation as possible be used for imaging. The recording material therefore must be capable of forming a latent image with a significantly low charge density upon brief X-ray exposure. The conventional silver halide photographic materials useful for medical radiography have provided a high degree of photosensitivity but have the disadvantage of not being room light handleable. Conventional commercial X-ray sensitive silver halide photographic materials also have been processed using processing solutions or baths, rather than dry processing.
Accordingly, there has been a continuing need for improved dry electrographic recording materials and processes which enable room light handleable imaging, ohmic resistivity within desired ranges, imaging that enables latent image amplification with improved speed, and dry processing.